为mapView恢复状态时,它会在保存期间略微缩小。我创建了一个iOS单视图应用程序,其中只包含一个填充整个视图的MKMapView来尝试对此进行故障排除。我的调试打印语句显示正在保存和恢复地图值,但跨度纬度或经度最终会发生变化。我错过了什么?
编辑:
这个问题与以下主题相同: MKMapView setRegion "snaps" to predefined zoom levels? MKMapView show incorrectly saved region
作为实验,我添加了一个MKCoordinateRegion类型的类变量,并将decodeRestorableState方法中读取的区域分配给它。我还为视图控制器添加了一个按钮和动作处理程序,它将mapView的区域设置为添加的变量的值。点击按钮时,地图会缩放到恢复期望的位置。我很奇怪,位置坐标在decodeRestorableState方法中工作不正确,但这些相同的坐标在按钮的动作处理程序中正常工作。
import UIKit
import MapKit
class ViewController: UIViewController {
@IBOutlet weak var mapView: MKMapView!
}
extension MKMapView {
override open func encodeRestorableState(with coder: NSCoder) {
super.encodeRestorableState(with: coder)
region.encodeRestorableState(with: coder)
camera.encodeRestorableState(with: coder)
}
override open func decodeRestorableState(with coder: NSCoder) {
super.decodeRestorableState(with: coder)
region.decodeRestorableState(with: coder)
camera.decodeRestorableState(with: coder)
}
}
extension MKCoordinateRegion {
private static let KEY_LATITUDE = "Region.latitude"
private static let KEY_LONGITUDE = "Region.longitude"
private static let KEY_WIDTH = "Region.spanWidth"
private static let KEY_HEIGHT = "Region.spanHeight"
func encodeRestorableState(with coder: NSCoder) {
coder.encode(center.latitude, forKey: MKCoordinateRegion.KEY_LATITUDE)
coder.encode(center.longitude, forKey: MKCoordinateRegion.KEY_LONGITUDE)
coder.encode(span.latitudeDelta, forKey: MKCoordinateRegion.KEY_HEIGHT)
coder.encode(span.longitudeDelta, forKey: MKCoordinateRegion.KEY_WIDTH)
}
mutating func decodeRestorableState(with coder: NSCoder) {
center.latitude = coder.decodeDouble(forKey: MKCoordinateRegion.KEY_LATITUDE)
center.longitude = coder.decodeDouble(forKey: MKCoordinateRegion.KEY_LONGITUDE)
span.latitudeDelta = coder.decodeDouble(forKey: MKCoordinateRegion.KEY_HEIGHT)
span.longitudeDelta = coder.decodeDouble(forKey: MKCoordinateRegion.KEY_WIDTH)
}
}
extension MKMapCamera {
private static let KEY_ALTITUDE = "Camera.altitude"
private static let KEY_HEADING = "Camera.heading"
private static let KEY_PITCH = "Camera.pitch"
private static let KEY_LATITUDE = "Camera.latitude"
private static let KEY_LONGITUDE = "Camera.longitude"
func encodeRestorableState(with coder: NSCoder) {
coder.encode(altitude, forKey: MKMapCamera.KEY_ALTITUDE)
coder.encode(heading, forKey: MKMapCamera.KEY_HEADING)
coder.encode(Double(pitch), forKey: MKMapCamera.KEY_PITCH)
coder.encode(centerCoordinate.latitude, forKey: MKMapCamera.KEY_LATITUDE)
coder.encode(centerCoordinate.longitude, forKey: MKMapCamera.KEY_LONGITUDE)
}
func decodeRestorableState(with coder: NSCoder) {
altitude = coder.decodeDouble(forKey: MKMapCamera.KEY_ALTITUDE)
heading = coder.decodeDouble(forKey: MKMapCamera.KEY_HEADING)
pitch = CGFloat(coder.decodeDouble(forKey: MKMapCamera.KEY_PITCH))
centerCoordinate.latitude = coder.decodeDouble(forKey: MKMapCamera.KEY_LATITUDE)
centerCoordinate.longitude = coder.decodeDouble(forKey: MKMapCamera.KEY_LONGITUDE)
}
}
有同样的问题。我的解决方法是在视图控制器的viewDidAppear中设置mapView.camera。
let mapCameraKey = "MapCameraKey"
var restoredCamera: MKMapCamera?
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
if let restoredCamera = restoredCamera {
mapView.camera = restoredCamera
}
}
override func encodeRestorableState(with coder: NSCoder) {
super.encodeRestorableState(with: coder)
coder.encode(mapView.camera, forKey: mapCameraKey)
}
override func decodeRestorableState(with coder: NSCoder) {
super.decodeRestorableState(with: coder)
restoredCamera = coder.decodeObject(forKey: mapCameraKey) as? MKMapCamera
}